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<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>

</body>
<script>
  // 字符串String
  function isString(e) {
    return typeof(e) == 'string' && e.constructor == String
  }
  console.log(isString(1))
  console.log(isString(''))
  console.log(isString(' '))
  console.log(isString('--'))
  console.log(isString(null))
  console.log(isString([]))
  console.log(isString(['2', 4]))


  let a = {
    b: 1
  }

  console.log(a.c)

  let ccc = [{
    name: '1'
  }]

  const handletemData = (data, e) => {
    return data.find((item) => item.name == e);
  };

  console.log(handletemData(ccc, '22'))


  console.log(parseFloat(undefined))

  console.log(typeof undefined == "string" && undefined.constructor == String)


  console.log(parseInt(undefined) / 4)

  let a1 = {
  b: 1,
  c: 0,
};
console.log("111", a1?.b);
console.log("222", a1?.c);
</script>

</html>